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| author | Prarit Bhargava <prarit@redhat.com> | 2017-12-04 11:45:21 -0500 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2017-12-07 10:28:22 +0100 |
| commit | 947134d9b00f342415af7eddd42a5fce7262a1b9 (patch) | |
| tree | 5b727713b606ec88fc5d085249526f48fa7c1dfb | |
| parent | 88edb57d1e0b262e669c5cad36646dcf5a7f37f5 (diff) | |
| download | linux-947134d9b00f342415af7eddd42a5fce7262a1b9.tar.bz2 | |
x86/smpboot: Do not use smp_num_siblings in __max_logical_packages calculation
Documentation/x86/topology.txt defines smp_num_siblings as "The number of
threads in a core". Since commit bbb65d2d365e ("x86: use cpuid vector 0xb
when available for detecting cpu topology") smp_num_siblings is the
maximum number of threads in a core. If Simultaneous MultiThreading
(SMT) is disabled on a system, smp_num_siblings is 2 and not 1 as
expected.
Use topology_max_smt_threads(), which contains the active numer of threads,
in the __max_logical_packages calculation.
On a single socket, single core, single thread system __max_smt_threads has
not been updated when the __max_logical_packages calculation happens, so its
zero which makes the package estimate fail. Initialize it to one, which is
the minimum number of threads on a core.
[ tglx: Folded the __max_smt_threads fix in ]
Fixes: b4c0a7326f5d ("x86/smpboot: Fix __max_logical_packages estimate")
Reported-by: Jakub Kicinski <kubakici@wp.pl>
Signed-off-by: Prarit Bhargava <prarit@redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jakub Kicinski <kubakici@wp.pl>
Cc: netdev@vger.kernel.org
Cc: "netdev@vger.kernel.org"
Cc: Clark Williams <williams@redhat.com>
Link: https://lkml.kernel.org/r/20171204164521.17870-1-prarit@redhat.com
| -rw-r--r-- | arch/x86/kernel/smpboot.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 05a97d5fe298..35cb20994e32 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -106,7 +106,7 @@ EXPORT_SYMBOL(__max_logical_packages); static unsigned int logical_packages __read_mostly; /* Maximum number of SMT threads on any online core */ -int __max_smt_threads __read_mostly; +int __read_mostly __max_smt_threads = 1; /* Flag to indicate if a complete sched domain rebuild is required */ bool x86_topology_update; @@ -1304,7 +1304,7 @@ void __init native_smp_cpus_done(unsigned int max_cpus) * Today neither Intel nor AMD support heterogenous systems so * extrapolate the boot cpu's data to all packages. */ - ncpus = cpu_data(0).booted_cores * smp_num_siblings; + ncpus = cpu_data(0).booted_cores * topology_max_smt_threads(); __max_logical_packages = DIV_ROUND_UP(nr_cpu_ids, ncpus); pr_info("Max logical packages: %u\n", __max_logical_packages); |